Field of the Invention
The present invention relates to a particularly microporous material comprising a stack or array of fibers, consolidated by a latex-based binder. This invention also relates to a process for producing such material and to various applications thereof.
The microporous material or component according to this invention is especially useful for the manufacture of microporous slab electrodes and separators, such as the diaphragms used for electrolysis.
Description of the Prior Art
It is known to this art that, as a general rule, the aforesaid microporous components must satisfy a number of requirements:
(a) they must have a controlled microporosity in respect of pore size and of pore size distribution;
(b) when they are used to fabricate the cathode component of a sodium chloride electrolysis cell, their thickness must be low, on the order of 0.1 mm to 5 mm, and at the same time they must have a high surface area which can exceed several m.sup.2.
Furthermore, these microporous materials must be capable of being produced by deposition on a rigid structure characterized by high aperture ratios.
Such microporous materials are typically produced by vacuum filtration of a suspension of fibers and binders.
A difficulty with this method of preparation lies in the fact that a major portion of the binder is introduced in the form of a latex, which latex is removed during the filtering operation.
This results not only in a loss of binder, but also in poor control of the amount which is retained, and, hence, of the consolidation and, ultimately, of the final characteristics of these microporous materials.
In order to introduce the microporosity into such materials, various fillers, such as alkali metal or alkaline earth metal-containing fillers, such as halides, sulfates, sulfites, bisulfites, phosphates, carbonates, bicarbonates, amphoteric alumina or silica, have already been proposed as pore-forming agents.
These pore-forming agents are at least partially removed, depending upon their chemical nature, by an acidic or alkaline medium.
Unfortunately, from a mechanical standpoint, these pore-forming agents have to be considered as factors in the disintegration of the microporous materials.